The present invention relates to the art of electrical potential determination. It finds particular application in determining true or absolute potential and measuring other electrostatic potentials on an absolute scale. It is to be appreciated that the present invention is applicable to monitoring potential and change in potential relative to a standard or absolute potential reference. The potential of earth-ground or other objects, such as aircraft, fluid or grain containers, chemical reaction tanks, hospital patients, and the like may be measured.
Historically, voltage measuring devices required two different electrostatic potentials in order to produce a measurement. It has been considered a common convenience and practical convention for engineers and scientists to use the Earth as a common reference point when measuring single point sources of potential. Earth-ground is arbitrarily assigned a zero potential. A convenient common reference for voltage measurements is provided by a metal rod driven into the ground, a connection to a metallic water pipe, a connection to a power line common ground wire, or the like.
There are inherent inaccuracies resultant from measuring potential with reference to earth-ground. The potential of the Earth changes with time and location. Telluric currents flow along the Earth on both land and water. Telluric currents result from storms, time-varying electromagnetic induction, and other natural and man-made causes. Thus, the potential of earth-ground varies with location on the surface of the Earth and with time.
Further, solar wind and energetic charged particles, often associated with sunspots, periodically flow over and immerse the Earth. Exposure of the Earth to a varying flux of charged particles can also be expected to alter the absolute potential of the Earth.
Within the atmosphere, the Earth is more negative than the surrounding atmosphere, which surrounding atmosphere in turn has an altitude dependent potential difference relative to the Earth. That is, the potential difference across the atmosphere of the Earth is about 400,000 volts. The potential difference tends to vary most quickly adjacent the Earth with a voltage variation on the order of 75 to 250 volts per meter. Pollution, humidity, snow, rain, and other atmospheric events cause variations in this potential difference.
Electronic equipment in aircraft is commonly grounded to the metal frame of the airplane and other vehicles. However, aircraft with time assume a potential more closely related to the potential of the surrounding atmosphere than to the potential of the Earth below. The potential differences between aircraft tend to manifest themselves in operations such as mid-air refueling, in which two aircraft come into physical, hence electrical contact.
There are other, apparently much greater voltage or potential differences within thunderstorm clouds. From investigations of lightning and thunderstorms, it appears that some clouds can be hundreds of millions of volts different from other clouds or the ground.
By arbitrarily assigning a zero potential value to earth-ground, the possibility that the Earth can have a finite and changing potential is ignored. Like birds on a power line, measurements relative to earth-ground are completely unaware of large changes in Earth potential. With a standard reference, changes in the Earth potential with time and/or location, can be measured. With a reference potential, changes in Earth potential could be measured analogous to temperatures on the Celsius scale with "zero" at a readily measurable event, i.e. the freezing point of water. In time perhaps this electrical standard can be extrapolated to an absolute zero potential in the sense of absolute zero on the Kelvin temperature scale.
There are a variety of "full moon" type phenomenon which may be related to changes in the supposedly zero Earth potential. These effects include the build-up of boiler scale, the rate of polymerization of colloidal systems, and others which tend to vary with the 28 day cycle of the moon. Solar winds also vary on a 28 day cycle, mimicking the cycle of the moon. Other phenomenon such as bleeding during surgery, migraine onset, and neurological disorders follow similar cyclic patterns. Monitoring changes in the Earth potential may also alleviate recalibration and drift problems in electronic equipment, spontaneous explosions of potentially explosive materials, gremlins in the electronics of aircraft, submarines, space vehicles during launch, and the like. Other effects of Earth potential change may include blood clotting times, negative air ion benefits, crop and market cycles, reproduction rates of bacteria, and the like.
Lorrain and Corson have calculated that an Earth surface charge of 8.16.times.10.sup.13 coulombs could generate the Earth's magnetic field. If one multiplies the charge density for a 0.9% sodium chloride solution observed using the present invention times a 1.664.times.10.sup.24 grams estimate of the total quantity of water in the hydrosphere, one obtains an electrostatic charge of 6.3.times.10.sup.13 coulombs, suggesting that the hydrosphere may well contain sufficient static charge to produce the Earth's magnetic field.
My earlier U.S. Pat. No. 4,839,581 issued Jun. 13, 1989 describes apparatus and techniques for measuring electrical potential. Although the apparatus described in the aforementioned patent was successful, it did have drawbacks, particularly in the area of long term drift when potential measurements were made repeatedly or intermittently over extended durations on the order of months and years. Another drawback with these prior apparatus is that their output readings were temperature dependent. The present application describes an apparatus and technique which enables an accurate determination of dielectric temperature coefficients which will provide a built-in temperature regulation.
Einstein's 1924 non-neutrality of matter hypothesis has been tested in the past, generally with equipment based on the Faraday "ice bucket" experiment. In the Faraday ice bucket experiment, an insulated pewter ice-pail was connected by a wire to a delicate gold-leaf electrometer. A round brass ball was hung from and insulated by a dry silk thread. The ice bucket and electrometer were perfectly discharged and the brass ball was charged when held some distance from the ice bucket. The brass ball was introduced into the volume of the ice bucket. When the brass ball had a positive charge, the electrometer diverged positively; when the brass ball was taken away, the electrometer collapsed perfectly. As the brass ball entered the ice bucket, the divergence of the electrometer increased until the brass ball was about 3 inches below the top edge of the ice pail. Thereafter, the divergence of the electrometer remained quite steady and unchanged for any greater depression into the ice pail. This was taken as showing that after this point, the inductive action of the brass ball is entirely exerted on the interior of the ice pail and not in any degree directly upon external objects. When the brass ball touched the bottom of the ice bucket, all of its charge was communicated to the ice pail; there is no longer any inductive action between the brass ball and the ice pail. Upon being withdrawn and examined, the brass ball was found to have been perfectly discharged.
Others have used Faraday cups to measure static charge. Keithley Instruments "Low Level Measurements" describes a test fixture for evaluating material for anti-static properties. A pair of conductive cups are mounted one inside the other separated by an insulator. A Model 617 electrometer is connected across the cups and set in the coulombs mode. An IC is placed in the tube and allowed to slide the length of the tube and fall into the Faraday cup. The amount of charge built up is registered by the electrometer. The test is typically repeated with the same IC and same length tubes of different materials. In this manner, different materials can be evaluated for anti-static protection.
The present invention contemplates a new and improved apparatus and measurement technique which overcomes the above-referenced problems and others.